Device for dressing profiled grinding wheels



Aug. 25,1942. F. TURRETTINI 2,294,003

DEVICE FOR DRESSING PROFILE!) GRINDING WHEELS Filed June 15,1940 2 Sheets-Sheet l g 24 a a Aug. 25, 1942. F. TURRETTlNl ,0

DEVICE FOR DRESSING PROFILED GRINDING WHEELS Filed June 15, 1940 2 Sheets-Shed 2 H6. 3 5 .Zim/v 2 zzz efiw J Patented Aug. 25, 1942 mzvics Fon DRESSING PROFILED GRIND- ING WHEELS Fernand Turrettini, Bellevue-Geneva, Switzerland, assignor to Societe Genevoise dlnstruments de Physique, Geneva, Switzerland, a firm i of Switzerland Application June 15, 1940, Serial No. 340,811

In Switzerland June 24, 1939 1 Claim.

The present invention relates to a device for dressing profiled grinding wheels, in particular wheels for grinding screw threads.

Grinding wheels used for this purpose are, generally speaking, constructed in the form of a double cone or two equally shaped truncated cones having their bases opposite each other, whereby an arc, of a circle of determined radius whose value depends upon the thread to be members, separate controls have to be actuated in a series of subsequent operations necessary for effecting the fiank-dressingand the roundingofi of the head of the profile. The result of this arrangement is an inconvenienthandling as also a considerable loss of time.

The object of the present invention is to avoid these inconveniences and to provide a device permitting to rapidly and easily eifect the different dressing operations on the grinding wheel. More specially the invention resides in the provision of an unique driving organ which controls the difierent movements of the dressing tool and which by reason of a sole continuous displacement causes the said tool to describe its complete path composed of two straight lines connected to each'other by an arc of a circle.

In order that this invention may be clearly understood and readily carried into practice reference may be had to the appended explanatory drawings showing, by way of example, a preferred embodiment of the invention.

Fig. 1 is a general sectional view of the whole device according to the invention.

Fig. 2 is a top plan view of said device.

Fig. 3 is a sectional view taken on the line III-III in Fig. 1, illustrating a detail.

Figs. 4' and 5 are examples of profiles of the grinding wheel, illustrating the operation of the device.

The represented trueing device comprises a slide 2 carried by-a body member l3 and beingdisplaceable forward and backward along a guide s of said member. An arm a is solidal with the said slide and extends upwardly therefrom, terminating at its free end in a holder It for a trueing diamond I intended to dress the profile of the grinding wheel W. The diamond is suitably supported in the holder 2b and can be easily and accurately adjusted therein with respect to the grinding wheel W so as to assume an initial working position and to be gradually advanced from this position for the subsequent dressing of said wheel. 5 designates arelatively short rack fixed to the inside of the slide 2 and meshingwith'a pinion t of a movement transmitting device which will be described later.

The body member I3 is fixedly mounted on a second body member M which afiords a pivot 20 rotatably supported. in the machine bed 21 by means of two vertically spaced low-friction bearings 2| and 22, such as ball or roller bearings. The body member l4 and pivot 20 are made of one piece and form together with the body member l3 the swivel base of the trueing device.

Between the slide 2 and the swivel base of the device is disposed a coil compression spring 23. As clearly shown in Fig. 3, this spring is lodged in a sheath 6 of the body member i3 and freely embraces a rod 26 extending entirely through said sheath and fixed at both ends to the slide 2. Each extremity of the spring 23 bears upon a ring:23& seated against a shoulder 26:: of said rod, the spring being set between the two rings 239. with a certain initial stress so as to assure a, rigid connection between the slide 2 and the swivel base l3, I l, 20. Owing to the low-friction bearings 2i and 22 employed for rotatably supporting the said swivel base on the machine bed 21, it is not necessary to provide for an excessively strong spring action; a spring of relatively light stress may be sufiicient to assure greatest reliability of service, as will later appear.

As clearly shown in Fig. l, the body member i3 is drilled transversely across its body for receiving a passing axle l the upper end of which carries the pinion t meshing with the rack 5 of the slide 2, while the lower end of said axle carries a pinion 8. Also the body member it and its pivot 20 are hole bored from end to end to accommodate an axle l0 carrying, on the one side, a pinion 9 meshing with the pinion 8 and, On the other side, a pinion H meshing with a pinion i2, the latter being fixed to a hand-wheel or handle not represented. Parts H, ill, 9, 8, i

and 5 constitute the movement transmitting device by means of which the slide 2 may be displaced forward and backward on the swivel base It, it, 20. In the present instance, the pinions II and I2 are shown having helicoidal toothings.

The pivotal movement of the base I3, ll, 20 is regulated by stops I5 and I6 as best seen in Fig. 2. The said stops can be displaced in a sunken circular guideway 28 on the machine bed 21, and they may be temporarily locked in said guideway in any desired position of angular adjustment with respect to the middle plane of the grinding wheel, a series of graduations I1 being provided on the bed 21 adjacent said guideway for determining the exact degree of displacement or angular-position of the two stops. l9 designates an anbutment piece rigid with the base I3, I4 20 and adapted to cooperate with the stops I5 and IS on the machine bed; it carries a pointer I8 sliding on the graduation I1.

The machine bed 21 is also provided with.a forked lever 24 which is mounted to revolve upon a short shaft 25 fixed to said bed, and said lever presents two arms 24a and 24s bent inwardly and being adapted to ,embrace the abutment piece I9-of the swivel base I3, I4, 20 for locking said base in the position shown in the drawings.

The operation of the described device is as follows:

To effect the rounding-oil of the head of the wheel profile, the pinion I2 is rotated in clockwise or counterclockwise direction by means of the hand-wheel or handle not represented and thereby transmits its movement through pinion II, axle I0, pinions 9 and 8, axle I, and pinion 4 to the rack 5 rigid with the slide 2. The latter is held in position by the coil spring 23 and will not be displaced with respect to the swivel base I3, I4, 20. In consequence, the whole device will rotate on the machine bed 21 about the geometric axis of the pivot '20 until the abutment piece I9 comes to abut against one of the two stops, for instance the stop I5, whereby the diamond I follows the arc of a circle 11-?) the center 0 of which lies on the geometric axis of the pivot 20 as best seen in Fig. 4.

As soon as the abutment piece I9 abuts the stop I5, the motive power transmitted to the. slide 2 through the medium of the above menj' tioned pinions and axles causes the said slide to be displaced against the action of the spring 23 which is then depressed, thereby allowing the diamond I to effect a translatory rectilinear movement tangential to the arc a-b for dressing the'right flank b-d shown in Fig. 4. The end d of this tangential stroke will be reached when the spring 23 has been completely depressed.

The pinion I2 is then rotated in the opposite direction whereby the translatory rectilinear movement of the diamond I is repeated from'b to a, while the spring 23 still presses the abutment piece I9 against the stop I5. When the slide 2 has returned to the normal position wherein the spring 23 retakes its initial tension, the former will again be fast to the swivel base I3, I4, 20 and the diamond I will dress the arc of circle in the reverse direction from b to a. Upon reaching the point a, the abutment piece I9 comes to abut against the other of said stops I6;

the spring 23 will be again depressed and the pivotal movement of the diamond will be converted in a translatory rectilinear movement for dressing the left flank a-e. It will thus be seen that the operation of the whole device is obtained simply by turning the pinion I2 in clockwise and counters-clockwise direction.

The desired radius of curvature r of the arc of circle 0-!) may be obtained by adjusting the cutting edge of the diamond I at a suitable distance from the'geometric axis of the pivot 20; moreover, the aperture angle or working range of the said axis may be determined by the angular adjustment of the stops l5 and IS.

The represented trueing device permits also dressing grinding wheels having a trapezoidal profile as shown in Fig. 5. In this case the wheel is first dressed in the same manner as hereinbefore described to receive a rounded profile as is shown by dotted lines in Figure 5. After this trueing operation is completed, the swivel base I3, I4, 20 is arrested in the middle plane of the grinding wheel by means of the forked lever 2| which is brought into the position shown in-the drawings, wherein it clamps the abutment piece IQ of said base between its two arms 24. and 24b. Then the pinion I2 is again rotated while simultaneously applying the diamond I against the rounded head of the wheel profile. In this way the said diamond is caused to reciprocate in a rectilinear movement parallel to the axis of rotation of the grinding wheel as indicated by the arrows f in Fig. 5, and at the same time it is advanced towards said axis for the subsequent cutting off of the rounding of the profile.

From the foregoing, it is believed that the construction and advantages of the present invention may be readily understood by those skilled in the art without further description, it being borne in mind that numerous changes may be made in the details disclosed without departing from the spirit of the invention as set out in the following claim.

What is claimed and desired to be secured by Letters Patent is:

In a grinding wheel ,truing apparatus intended in particular for screw thread grinding machines, in combination, a sliding tool-holder, an inner rack mounted inside the slide of said sliding toolholder, 9. base supporting the latter, an inner spring-box mounted in said base and linked with said sliding tool-holder and tending to keep it in neutral position, a pinion engaging said inner rack and mounted on an axle turning freely in said base, reduction gears linking said axle with a driving shaft mounted coaxially in pivot of saidflbase, roller bearings mounted on supporting bed and carrying said pivot, a coaxial semi-circular division traced on said bed, adjustable stops along said division, a fixed lug on said base cooperating directly with said stops, and a retractable intermediate stop and clamp "cooperating with said fixed lug to set the base for cylinder truing.

FERNAND TURRE'I'IINI. 

